Austrarchaea nodosa McPherson Range Assassin Spider (Forster, 1956)

Rix, Michael G. & Harvey, Mark S., 2011, Australian Assassins, Part I: A review of the Assassin Spiders (Araneae, Archaeidae) of mid-eastern Australia, ZooKeys 123, pp. 1-100 : 12-15

Austrarchaea nodosa McPherson Range Assassin Spider (Forster, 1956) Figs 1A-B5D7I8I1028

Archaea nodosa Forster, 1956: 151, figs 1-7.

Austrarchaea nodosa (Forster): Forster & Platnick, 1984: 21, figs 4-6, 9-10, 19, 27, 34-35, 57, 60-65.

Type material.

Holotype juvenile: Lamington National Park, Tullawallal [Antarctic Beech forest], south of Binna Burra, Queensland, Australia, [28°12'20"S, 153°11'20"E], from moss, 31.X.1955, T. Woodward (QMB W1955).

Other material examined.

AUSTRALIA: Queensland:Lamington National Park: Binna Burra, track to Tullawallal Antarctic Beech forest, 28°12'20"S, 153°11'20"E, sifting and teasing low vegetation, 7.IV.2006, M. & A. Rix, 1♂, 2 juveniles (WAM T89592DNA: LAM-51-J); Binna Burra, 11.II.1971, Y. Lubin, R. Raven, V. Davies, 1♀ (QMB S73925); Binna Burra, Ships Stern Circuit track, 28°11'51"S, 153°11'28"E, sifting elevated leaf litter, subtropical rainforest, 764 m, 25.IV.2010, M. & A. Rix, D. & S. Harms, J. Wojcieszek, 1 juvenile (WAM T112571DNA: Ar56-58-J); IBISCA Plot IQ-1100-A, 28°15'29"S, 153°09'32"E, bark spray, 1141 m, 11.III.2007, G. Thompson, A. Marcora, 1♂, 1♀, 1 juvenile (QMB S75416). New South Wales:Border Ranges National Park: Upper Brindle Creek, Wiangarie, 28°23'S, 153°06'E, pyrethrum, Nothofagus rainforest, 840 m, 15.XII.2008, G. Monteith, 1♀ (QMB S87983). Mount Warning National Park: 1975-1976, G. & S. Monteith, 1 juvenile (QMB S20426); Mount Warning, track to summit, 28°24'08"S, 153°16'27"E, sifting elevated leaf litter under Xanthorrhoea , wet eucalypt forest bordering subtropical rainforest, 728 m, 26.IV.2010, M. Rix, 1 juvenile (WAM T112572DNA: Ar57-46-J); off Mount Warning Road, 28°23'51"S, 153°17'20"E, sifting elevated leaf litter, subtropical rainforest, 348 m, 26.IV.2010, D. Harms, 1 juvenile (WAM T112573DNA: Ar58-53-J).

Additional material examined (of tentative identification).

AUSTRALIA: Queensland: Lamington National Park: Mount Hobwee, in moss, 3.IV.1976, R. Raven, 1 juvenile (QMB S30827); Nagarigoon, 8.IV.1976, 1 juvenile (QMB S30817). Mount Chinghee National Park: QM Berlesate, stick brushing, 17.XII.1982, G. Monteith, D. Yeates, G. Thompson, 1 juvenile (QMB S30804). New South Wales:Border Ranges National Park: Border Fence, Levers Plateau, via Rathdowney, pitfall trap, 670 m, 22.V.-IX.1976, G. & S. Monteith, 1 juvenile (QMB S30823).

Additional material (not examined).

AUSTRALIA: Queensland: Lamington National Park: Tullawallal Antarctic Beech forest, south of Binna Burra, 28°12'39"S, 153°11'32"E, Nothofagus rainforest, 900 m, 21.III.2006, C. Griswold, D. Silva, R. Raven, B. Baehr, M. Ramírez, 1♂ (CASENT 9018966); Binna Burra, 27.III.1976, R. Raven, V. Davies, 1♀, 1 juvenile (QMB S30820); Binna Burra, 28°11'38"S, 153°11'13"E, rainforest, 790 m, 21-23.III.2006, C. Griswold, D. Silva, R. Raven, B. Baehr, M. Ramírez, 1 juvenile (CASENT 9018963); Binna Burra, 28°11'38"S, 153°11'13"E, Berlese of leaf litter, rainforest, 790 m, 23.III.2006, C. Griswold, D. Silva, R. Raven, B. Baehr, M. Ramírez, 1 juvenile (CASENT 9018964); Binna Burra, along Border Track, 28°11'56"S, 153°11'15"E, beating vegetation, 900 m, 29-30.IV.2009, H. Wood, 1♂ (CASENT 9028426); same data, 1♂ (CASENT 9028388); O'Reillys, 25-26.IX.1986, J. Gallon, R. Raven, 1♀ (QMB S30814).

Diagnosis.

Austrarchaea nodosa can be distinguished from all other Archaeidae from mid-eastern Australia by the broad, flanged proximal portion of the embolic sclerite (Figs 10D-E; see also Forster and Platnick 1984, figs 61, 63) and the unique shape of the conductor (Figs 10D-E), which is thin, gently-tapered and slightly bent along its distal half. The presence of a shallow concave depression near the posterior margin of the ‘head’ (Fig. 7I) can also be used to distinguish females from most other species, including the sympatric Austrarchaea dianneae sp. n.

This species can also be distinguished from other genotyped taxa from mid-eastern Australia (see Fig. 3B) by the following seven unique nucleotide substitutions for COI (n = 4): A(42), C(393), C(639), C(939), A(960), A(1038), A(1053).

Description.

Male (QMB S30817): Total length 3.18; leg I femur 3.01; F1/CL ratio 2.70. Cephalothorax dark reddish-brown; legs tan-brown with darker annulations; abdomen mottled grey-brown and beige, with darker reddish-brown dorsal scute and sclerites (Fig. 10B). Carapace very tall (CH/CL ratio 2.30); 1.12 long, 2.56 high, 1.08 wide; ‘neck’ 0.56 wide; bearing two pairs of rudimentary horns; highest point of pars cephalica (HPC) near middle of ‘head’ (ratio of HPC to post-ocular length 0.57), carapace with shallow concave depression posterior to HPC; ‘head’ not strongly elevated dorsally (post-ocular ratio 0.24) (Fig. 8I). Chelicerae with short brush of accessory setae on anterior face of paturon (Fig. 10C). Abdomen 1.64 long, 1.13 wide; with three pairs of dorsal hump-like tubercles (HT 1-6); dorsal scute fused anteriorly to epigastric sclerites, extending posteriorly to first pair of hump-like tubercles; HT 3-6 each covered by separate dorsal sclerites. Unexpanded pedipalp (WAM T89592) (Figs 10D-F) with thin, pointed conductor, gently-tapered and slightly bent along distal half; embolic sclerite with broad, flanged proximal portion overlying proximal conductor; tegular sclerite 1 (TS 1) long, filiform, with sinuous distal tip, visible in retrolateral view; TS 2 spiniform, shorter than TS 1; TS 2a sinuous, largely obscured by TS 2; TS 3 indistinct, embedded within distal haematodocha, barely visible beyond retro-distal rim of tegulum.

Female (QMB S30817): Total length 3.54; leg I femur 3.01; F1/CL ratio 2.40. Cephalothorax dark reddish-brown; legs tan-brown with darker annulations; abdomen bi-coloured grey-brown and beige, palest posteriorly (Fig. 10A). Carapace tall (CH/CL ratio 2.12); 1.26 long, 2.67 high, 1.15 wide; ‘neck’ 0.64 wide; bearing two pairs of rudimentary horns; highest point of pars cephalica (HPC) near posterior third of ‘head’ (ratio of HPC to post-ocular length 0.63), carapace with shallow concave depression posterior to HPC; ‘head’ not strongly elevated dorsally (post-ocular ratio 0.23) (Fig. 7I). Chelicerae without accessory setae on anterior face of paturon. Abdomen 2.15 long, 1.64 wide; with three pairs of dorsal hump-like tubercles (HT 1-6). Internal genitalia with cluster of ≤ 12 variably shaped spermathecae on either side of gonopore, clusters meeting near midline of genital plate (Figs 5D, 10G); innermost (anterior) spermathecae longest, sausage-shaped, curved antero-laterally; outermost (posterior) spermathecae bulbous; other spermathecae variably pyriform, straight, directed antero-laterally.

Variation: Males (n=2): total length 2.97-3.18; carapace length 1.12-1.13; carapace height 2.56-2.67; CH/CL ratio 2.30-2.36. Females (n=3): total length 3.54-4.00; carapace length 1.21-1.33; carapace height 2.49-2.87; CH/CL ratio 2.06-2.15.

Distribution and habitat.

Austrarchaea nodosa is known from rainforest habitats along the McPherson Range and 'scenic rim’ of extreme south-eastern Queensland and north-eastern New South Wales, in the Lamington, Border Ranges and Mount Warning National Parks (Fig. 28). At Binna Burra (Lamington National Park) it has been found in sympatry with Austrarchaea dianneae sp. n., in the only known example of two-species sympatry among Australian archaeids (see Nomenclatural Remarks, below).

Conservation status.

This species has a relatively widespread distribution in several National Parks protected under World Heritage legislation, and is not considered to be of conservation concern.

Nomenclatural remarks.

The holotype specimen of Austrarchaea nodosa , described by Forster (1956), is a juvenile (probably penultimate) female from the Tullawallal Nothofagus forest near Binna Burra, Lamington National Park. Although long assumed to have only a single species, the greater Binna Burra region is now the only locality in Australia known to have two species of Archaeidae living in close sympatry: numerous specimens of Austrarchaea dianneae sp. n. were discovered near Binna Burra in April 2010, along the 'Ships Stern Circuit Track’, along with one juvenile specimen of Austrarchaea nodosa . Both Austrarchaea dianneae sp. n. and Austrarchaea nodosa are closely related (Fig. 3B) rainforest-dwelling taxa, rendering the identification of Forster’s holotype specimen - and therefore the identification of the generic type species - questionable. To address this issue, and to determine which species was actually described by Forster (1956), two lines of evidence are discussed below.

‘Tullawallal’ - the type locality cited by Forster (1956) - is a well-known, high-altitude Nothofagus moorei cool-temperate rainforest, situated off Binna Burra’s 'Border Track’ at around 900 m elevation. The dominant rainforest surrounding Tullawallal is a closed, complex notophyllous vine forest (with isolated warm-temperate and cool-temperate elements), typical of higher elevations throughout the Lamington National Park and McPherson Range (Fig. 28C). In all of the higher-altitude and/or closed rainforests of the Lamington Plateau and Border Ranges National Park, only identifiable specimens of Austrarchaea nodosa (as recognised above) have so far been collected. Furthermore, the two male specimens collected at or near Tullawallal (WAM T89592, CASENT 9018966) are also both Austrarchaea nodosa as here recognised. In contrast, the three localities where Austrarchaea dianneae sp. n. has been found (i.e. along the 'Ships Stern Circuit Track’ near Binna Burra, Wojigumal Creek, and in the Tamborine National Park) are significantly lower in altitude than Tullawallal and the surrounding 'Border Track’ region of Binna Burra (764 m, 570 m and 313 m, respectively), with more open ‘mixed’ rainforests and emergent eucalypts at the Binna Burra and Mount Tamborine localities (Fig. 29C).

Secondly, female specimens of both species possess a distinctive ‘head’ morphology; females of Austrarchaea nodosa (as here recognised) are characterised by a shallow concave depression posterior to the highest point of the pars cephalica (HPC) (Fig. 7I), whereas females of Austrarchaea dianneae sp. n. have no such depression and a significantly more pronounced posterior margin of the ‘head’ (Fig. 7H). The holotype juvenile specimen of Austrarchaea nodosa has a clear concave depression posterior to the HPC, and ‘head’ proportions otherwise very similar to the female illustrated in Figure 7I. In contrast, the only known penultimate female specimen of Austrarchaea dianneae sp. n., collected from near Binna Burra (WAM T112556), does not have a concave depression posterior to the HPC, and ‘head’ proportions otherwise similar to the allotype female Austrarchaea dianneae sp. n. illustrated in Figure 7H.

Clearly, given the identification of specimens collected from the type locality and similar nearby habitats, and the morphology of the holotype juvenile specimen, we are as confident as possible in newly-diagnosing Austrarchaea nodosa as the species described above, given an otherwise highly precarious nomenclatural situation.